The present invention generally relates to the testing of IC chips, and more particularly relates to devices for maintaining the temperature of an integrated circuit (IC) device under test (DUT).
Testing IC chips under thermally controlled conditions requires that a certain temperature be maintained for the DUT, which usually requires raising or lowering the DUT's temperature during the course of the test. Thermal control units have been devised for this purpose. Such units provide thermal contact with the DUT and carry heat away from or add heat to the DUT as required based on a predetermined set point temperature. Such units frequently use a peltier device as a heat pump to achieve such temperature control. Peltier devices are solid-state devices that come in small thin geometries and that can be controlled by a DC current to pump heat away from a contacted device for removal. By reversing the current, the Peltier device act as a heater by pumping heat into a contacted device.
In thermal control units for IC testing, the ability of the peltier device to efficiently transfer heat to and away from the DUT is affected by the contact between the Peltier device and the other components of the thermal control unit, including the thermal sensor containing pedestal that contacts the DUT. Efficient heat transfer requires large forces pushing the heat transfer surfaces of the Peltier device, typically forces that exceed 100 psi. The rigid mechanical designs heretofore used in DUT thermal control units to generate these required clamping forces tend to cause the components of the unit to bend or bow in a manner that interferes with thermal contacts made with the Peltier device, resulting in a degradation in the heat transfer capabilities of the device. The present invention is directed at overcoming these problems and to providing a thermal control unit that can have other beneficial features.